Institutional organizations, such as public safety organizations, typically use specialized voice communication systems embodied as narrowband radio systems. These narrowband systems typically support low-bit-rate digital or analog transmission of audio and/or data streams. An example of such a voice communication system is a Project 25 (P25)-compatible two-way Push-To-Talk voice communication system that includes wireless and wired voice communication devices. The voice communication devices may be, for example, portable narrowband two-way radios, mobile radios, dispatch consoles, or other similar voice communication entities that communicate with one another via wired and/or wireless networks. Institutional organizations choose these types of voice communications systems because they provide improved end-to-end voice quality and efficient group communication, use advanced cryptography, enable centralized logging of calls, and/or are associated with lower delay and higher reliability.
In parallel, institutional users may also use broadband communication systems to access public safety data applications. An example of such a broadband system is a wireless data network that operates in accordance with the Long Term Evolution (LTE) signaling standard and that includes wireless and wired communication devices. Broadband systems typically support high-bit-rate digital transmission of data streams, including real-time video. Bandwidth requirements of a broadband system are generally much greater than that required for a narrowband system and the radio frequency (RF) range of a broadband system is generally smaller than that of a narrowband system. Narrowband coverage is already widely deployed for mission critical use and is typically guaranteed for large percentages of given geographical areas, such as cities, counties and/or states. Although broadband systems are being rapidly deployed, there are likely to be gaps in broadband coverage in some areas that are already covered by narrowband systems.
In order to communicate on both a broadband system and a narrowband system, a communication device typically incorporates separate interfaces for each system. The communication device is configured to operate each interface on independent wireless links. For example, the communication device may operate on a Common Air Interface for a P25 system and a Uu interface for an LTE system. Information obtained from both interfaces is aggregated and processed by applications (also referred to as application clients or simply as clients) residing within the communication device. This enables a subscriber to maintain voice communications using, for example, an existing narrowband P25 system, while being able to access data applications using a broadband connection. Due to expected gaps in broadband coverage in some areas and in order to leverage the mature coverage and relatively advanced deployment of narrowband systems, in a current implementation, some low-bit-rate digital or analog data applications may be kept on narrowband systems, while new services that demand large throughput (e.g. radio software re-programming) are set up to operate on the broadband systems.
The communication device could be either one device with two network interfaces or it could be two separate devices with local connectivity between them. If two separate devices are used, each device will provide wide area connection to either the narrowband system or the broadband system. The local connectivity (which could be wirelesses or wired) between the separate devices would provide application clients on the communication devices with access to both wide-area communications links.
Whether operating via a broadband and/or narrowband interface, application client(s) residing within the communication device, in general, need to communicate with application server(s) located on a network. In order to provide the connectivity and ability for applications on the network to connect with clients on the communication device, the applications on the network need to have real-time knowledge of when there is a connection to the communication device. The applications on the network must also know what type of connection is viable at a given time. Both the broadband and narrowband networks are assumed to have an aggregated point, for example, a unified network service-layer routing, that provides a unified view and functionality to all applications in the network. In particular, a presence entity in the network service-layer routing provides the status of each communication device connected to the service-layer routing and the interface(s) for connecting with each communication device at a given time. This availability information allows applications on the network to determine, for example, what type of services to provide and the format of information to be sent to each connected communication device. As both the broadband and narrowband systems have their own coverage areas, the connection status of one or both interfaces may change as the communication device moves throughout a geographical area.
A current implementation requires constant exchanges of “heart-beat” messages between each communication device interface and the presence server to keep the presence server informed of the communication device connectivity status on the broadband and narrowband systems. This messaging exchange takes place on each respective interface and is typically more frequent over the broadband connection as the communication device is more likely to move in and out of broadband network coverage areas. The messaging exchange has a significant negative impact on the battery life in the communication device. Operating multiple interfaces on the communication device, in addition to potentially having the communication device connected via local wireless personal connection, requires that the communication device have a large battery. This increases the cost associated with the communication device and is likely to negatively impact the use time on a single battery charge. The “heart-beat” messages required for each operating subscriber also results in high traffic load on the network and reduces available network capacity.
Accordingly, there is a need for an improved method and apparatus for maintaining accurate connectivity status for a dual mode communication device while enabling efficient battery use on the communication device.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.